Electrode for battery, battery having electrode and method for manufacturing electrode and battery having electrode

ABSTRACT

Provided is an electrode for a battery which effectively suppress a short circuit between a positive electrode and a negative electrode at high temperature of the battery. 
     The electrode includes a current collector  110 , an active material layer  111  formed on at least one side of the current collector  110  and an insulating layer  112  formed on the surface of the active material layer  111 . The electrode was formed so that peeling occurs between the current collector  110  and the active material layer  111  and the peeling strength was 10 mN/mm or more when a 90° peeling test was performed at a peeling rate of 100/min.

TECHNICAL FIELD

The present invention relates to an electrode for a battery and a methodfor manufacturing the electrode, and in particular, to an electrodehaving an insulating layer on an active material layer and the like.

BACKGROUND ART

Secondary batteries are widely used as power sources for portableelectronic devices such as smart phones, tablet computers, notebookcomputers, digital cameras, and the like. In addition, secondarybatteries have been expanding their application as power sources forelectric vehicles and household power supplies. Among them, sincelithium ion secondary batteries are high in energy density and light inweight, they are indispensable energy storage devices for current life.

A conventional battery including a secondary battery has a structure inwhich a positive electrode and a negative electrode, which areelectrodes, are opposed to each other with a separator interposedtherebetween. The positive electrode and the negative electrode eachhave a sheet-like current collector and active material layers formed onboth sides of the current collector. The separator serves to prevent ashort circuit between the positive electrode and the negative electrodeand to effectively move ions between the positive electrode and thenegative electrode. Conventionally, a polyolefin system microporousseparator made of polypropylene or polyethylene material is mainly usedas the separator. However, the melting points of polypropylene andpolyethylene materials are generally 110° C. to 160° C. Therefore, whena polyolefin system separator is used for a battery with a high energydensity, the separator melts at a high temperature of the battery, and ashort circuit may occur between the electrodes in a large area.

Therefore, in order to improve the safety of the battery, it has beenproposed to form an insulating layer which is a substitute for aseparator in at least one of the positive electrode and the negativeelectrode. For example, Patent Literature 1 (Japanese Patent Laid-OpenNo. 2009-43641) discloses a negative electrode for a battery in which anegative electrode active material layer is formed on a surface of anegative electrode current collector, and a porous layer is formed onthe surface of the negative electrode active material layer. Similarly,Patent Literature 2 (Japanese Patent Laid-Open No. 2009-301765)discloses an electrode in which a porous protective film is provided ona surface of an active material layer formed on a current collector.Patent Literature 3 (Japanese Patent No. 5454295) discloses a method inwhich two or more paste layers are overlaid on a core material (currentcollector) of a positive electrode or a negative electrode, and then thepaste layer is dried to form a positive electrode plate or a negativeelectrode.

Generally, the active material layer is formed on the current collectoras follows. First, a long current collector foil wound on a roll isprepared as a current collector and a slurry for forming an activematerial layer is prepared. The slurry for forming the active materiallayer is a slurry obtained by dispersing fine particles of an activematerial and a binder in a solvent. Then, while feeding the currentcollector foil from the roll, the slurry for forming the active materiallayer is applied to the surface of the current collector foil by meansof a die coater or the like. After applying the slurry for formingactive material layer, the slurry for forming active material layer isdried and compression-molded, whereby the active material layer isformed on the surface of the current collector.

The insulating layer on the surface of the active material layer can beformed in the same manner as the formation of the active material layer.That is, a slurry for forming an insulating layer in which fineparticles of an insulating material and a binder are dispersed in asolvent is applied to the surface of the active material layer, and thenthe slurry is dried and compression-molded. Thereby, the insulatinglayer is formed on the surface of the active material layer.

CITATION LIST Patent Literature Patent Literature 1: Japanese PatentLaid-Open No. 2009-43641 Patent Literature 2: Japanese Patent Laid-OpenNo. 2009-301765 Patent Literature 3: Japanese Patent No. 5454295 SUMMARYOF INVENTION Technical Problem

However, in the above-described conventional electrode, when thetemperature of the battery becomes high and the separator shrinks in thein-plane direction, there was a possibility that the insulating layerwas dragged by the separator and peeled off from the active materiallayer to expose the active material layer. When the active materiallayer is exposed, it causes a short circuit between the positiveelectrode and the negative electrode. In addition, at high temperature,shrinkage force in the in-plane direction also acts on the activematerial layer itself and the insulating layer itself. Therefore, whenthe adhesion between the current collector and the active material layeris weak, the active material layer separates from the surface of thecurrent collector and shrinks, and a part of the surface of the currentcollector is exposed. Alternatively, when the adhesion between theactive material layer and the insulating layer is weaker than theadhesion between the active material layer and the current collector,although the adhesion between the active material layer and the currentcollector is maintained and shrinkage of the active material layer doesnot occur, there is a possibility that the insulating layer separatesfrom the surface of the active material layer and shrinks, and a part ofthe active material layer is exposed.

An object of the present invention is to provide an electrode having anactive material layer and an insulating layer on a current collector anda method for manufacturing the electrode in which the electrode iscapable of suppressing the occurrence of a short circuit even when theelectrode is assembled as a battery and used to reach a hightemperature.

Solution to Problem

According to one aspect of the present invention,

an electrode for a battery comprising:

a current collector,

an active material layer formed on at least one surface of the currentcollector,

an insulating layer formed on a surface of the active material layer,and

wherein peeling occurs between the current collector and the activematerial layer and a peeling strength thereof is 10 mN/mm or more when a90° peeling test is carried out at a peeling rate of 100 mm/min isprovided.

According to the other aspect of the present invention,

a battery comprising:

at least one positive electrode,

at least one negative electrode disposed to face the positive electrode,and

wherein at least one of the positive electrode and the negativeelectrode includes a current collector, an active material layer formedon at least one surface of the current collector, and an insulatinglayer formed on a surface of the active material layer, and peelingoccurs between the current collector and the active material layer and apeeling strength thereof is 10 mN/mm or more when a 90° peeling test iscarried out at a peeling rate of 100 mm/min is provided.

The present invention further provides a method for manufacturing anelectrode for a battery, the method comprising;

forming an active material layer on at least one surface of a currentcollector,

forming an insulating layer such that the insulating layer is finallylaminated on a surface of the active material layer, and

wherein at least one of a material of the active material layer, aformation condition of the active material layer, a material of theinsulating layer and a formation condition of the insulating layer isdetermined such that peeling occurs between the current collector andthe active material layer and a peeling strength thereof is 10 mN/mm ormore when a 90° peeling test is carried out at a peeling rate of 100mm/min.

Definition of Terms Used in the Present Invention

“90° peeling test” refers to a test of obtaining peeling strength fromthe maximum load applied to a sample before the sample peels off whenthe sample prepared from an electrode having an active material layerand an insulating layer formed on the surface of a current collector wasfixed on the surface of a sample table, and the sample was peeled fromthe sample table at a peeling rate of 100 mm/min while holding one endportion of the fixed sample and keeping the peel angle at 90°. In thepresent invention, the “90° peeling test” is carried out under anambient temperature environment (15° C. to 25° C.). As the sample, anelectrode cut into a width of 20 mm and a length of 100 mm is used. Forfixing the sample to the sample table, the surface on which the activematerial layer and the insulating layer are formed is fixed to thesample table. At this time, only the portion of the sample from the oneend to 80 mm in the longitudinal direction is fixed, and a portion ofthe sample not fixed is set as a grip margin by a chuck or the like atthe time of peeling the sample. The method of fixing the sample to thesample table is not particularly limited as long as the sample can befixed so that the insulation layer does not peel from the sample tablewhen the sample is peeled off. For fixing the sample, for example,double-sided tape can be used.

“Peeling strength” is expressed as a value obtained by dividing themaximum load measured in the “90° peeling test” by the width of thesample of 20 mm and converting it into force per 1 mm of the samplewidth.

Advantageous Effects of Invention

According to the present invention, a short circuit between the positiveelectrode and the negative electrode at high temperature can beeffectively suppressed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded perspective view of a battery according to oneembodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of an electrode assemblyshown in FIG. 1.

FIG. 3 is a schematic cross-sectional view for explaining the structuresof the positive electrode and the negative electrode shown in FIG. 2.

FIG. 4A is a cross-sectional view showing an example of arrangement ofthe positive electrode and the negative electrode in the electrodeassembly.

FIG. 4B is a cross-sectional view showing another example of arrangementof the positive electrode and the negative electrode in the electrodeassembly.

FIG. 4C is a cross-sectional view showing still another example ofarrangement of the positive electrode and the negative electrode in theelectrode assembly.

FIG. 5 is an exploded perspective view of a battery according to anotherembodiment of the present invention.

FIG. 6 is a schematic view of one embodiment of an electrodemanufacturing apparatus according to the present invention.

FIG. 6A is a plan view of a current collector at the stage ofintermittently applying an active material layer on the currentcollector for explaining a manufacturing process of an electrodeaccording to one embodiment of the present invention.

FIG. 6B is a plan view of a current collector at the stage of furtherapplying an insulating layer on the active material layer on the currentcollector for explaining a manufacturing process of an electrodeaccording to one embodiment of the present invention.

FIG. 6C is a plan view illustrating a cutting shape in a stage ofcutting a current collector applied the active material layer and theinsulating layer into a desired shape for explaining a manufacturingprocess of an electrode according to one embodiment of the presentinvention.

FIG. 7 is a schematic view of another embodiment of the electrodemanufacturing apparatus according to the present invention.

FIG. 8 is a schematic view showing an embodiment of an electric vehicleequipped with a battery.

FIG. 9 is a schematic diagram showing an example of a power storagedevice equipped with a battery.

DESCRIPTION OF EMBODIMENTS

Referring to FIG. 1, an exploded perspective view of a battery 1according to one embodiment of the present invention is shown, whichcomprises an electrode assembly 10 and a casing enclosing the electrodeassembly 10 together with an electrolyte. The casing has casing members21, 22 that enclose the electrode assembly 10 from both sides in thethickness direction thereof and seal outer circumferential portionsthereof to thereby seal the electrode assembly 10. A positive electrodeterminal 31 and a negative electrode terminal 32 are respectivelyconnected to the electrode assembly 10 with protruding part of them fromthe casing.

As shown in FIG. 2, the electrode assembly 10 has a configuration inwhich a plurality of positive electrodes 11 and a plurality of negativeelectrodes 12 are disposed so as to be alternately positioned. Betweenthe positive electrode 11 and the negative electrode 12, a separator 13for preventing short-circuiting between the positive electrode 11 andthe negative electrode 12 while securing ionic conduction between thepositive electrode 11 and the negative electrode 12 is arranged asnecessary according to the structure of the positive electrode 11 andthe negative electrode 12 described below.

Structures of the positive electrode 11 and the negative electrode 12will be described with further reference to FIG. 3. In the structureshown in FIG. 3, the positive electrode 11 and the negative electrode 12are not particularly distinguished, but the structure is applicable toboth the positive electrode 11 and the negative electrode 12. Thepositive electrode 11 and the negative electrode 12 (collectivelyreferred to as “electrode” in a case where these are not distinguished)include a current collector 110 which can be formed of a metal foil, anactive material layer 111 formed on one or both surfaces of the currentcollector 110. The active material layer 111 is preferably formed in arectangular shape in plan view, and the current collector 110 has ashape having an extended portion 110 a extending from a region where theactive material layer 111 is formed.

The extended portion 110 a of the positive electrode 11 and the extendedportion 110 a of the negative electrode 12 are formed at positions notoverlapping each other in a state where the positive electrode 11 andthe negative electrode 12 are laminated. However, the extension portions110 a of the positive electrodes 11 are positioned to overlap with eachother, and the extension portions 110 a of the negative electrodes 12are also similar to each other. With such arrangement of the extendedportions 110 a, in each of the plurality of positive electrodes 11, therespective extended portions 110 a are collected and welded together toform a positive electrode tab 10 a. Likewise, in the plurality ofnegative electrodes 12, the respective extended portions 110 a arecollected and welded together to form a negative electrode tab 10 b. Apositive electrode terminal 31 is electrically connected to the positiveelectrode tab 10 a and a negative electrode terminal 32 is electricallyconnected to the negative electrode tab 10 b.

At least one of the positive electrode 11 and the negative electrode 12further includes an insulating layer 112 formed on the active materiallayer 111. The insulating layer 112 is formed in a region where theactive material layer 111 is not exposed in plan view. In the case wherethe active material layer 111 is formed on both surfaces of the currentcollector 110, the insulating layer 112 may be formed on both of theactive materials 111, or may be formed only on one of the activematerials 111.

What is important here is that when a 90° peeling test is carried outwith a sample cut out with an electrode having the active material layer111 and the insulating layer 112 on the current collector 110 with awidth of 20 mm at a peeling rate of 100 mm/min, peeling occurs betweenthe current collector 110 and the active material layer 111, and itspeeling strength is 10 mN/mm or more. Peeling between the currentcollector 110 and the active material layer 111 during the 90° peelingtest means that the peeling strength between the active material layer111 and the insulating layer 112 is higher than the peeling strengthbetween the current collector 110 and the active material layer 111. Byspecifying the peeling strength between the current collector 110, theactive material layer 111 and the insulating layer 112 in this manner,even when the battery becomes high in temperature when used as abattery, the positive electrode and the negative electrode can beeffectively suppressed.

Some examples of the arrangement of the positive electrode 11 and thenegative electrode 12 having such a structure are shown in FIGS. 4A to4C. In the arrangement shown in FIG. 4A, the positive electrode 11having the insulating layer 112 on both sides and the negative electrode12 not having the insulating layer are alternately laminated. In thearrangement shown in FIG. 4B, the positive electrode 11 and the negativeelectrode 12 having the insulating layer 112 on only one side arealternately laminated in such a manner that the respective insulatinglayers 112 do not face each other. In the structures shown in FIGS. 4Aand 4B, since the insulating layer 112 exists between the positiveelectrode 11 and the negative electrode 12, the separator 13 (see FIG.2) can be omitted.

On the other hand, in the arrangement shown in FIG. 4C, the positiveelectrode 11 having the insulating layer 112 on only one side and thenegative electrode 12 not having the insulating layer are alternatelylaminated. In this case, the separator 13 is required between thepositive electrode 11 and the negative electrode 12 opposed to thesurface not having the insulating layer 112. However, since theseparator 13 can be omitted between the positive electrode 11 and thenegative electrode 12 opposed to the surface having the insulating layer112, the number of the separators 13 can be reduced.

The structure and arrangement of the positive electrode 11 and thenegative electrode 12 are not limited to the above examples and variousmodifications are possible as long as the insulating layer 112 isprovided on at least one surface of at least one of the positiveelectrode 11 and the negative electrode 12. For example, in thestructures shown in FIGS. 4A to 4C, the relationship between thepositive electrode 11 and the negative electrode 12 can be reversed.

Since the electrode assembly 10 having a planar laminated structure asillustrated has no portion having a small radius of curvature (a regionclose to a winding core of a winding structure), the electrode assembly10 has an advantage that it is less susceptible to the volume change ofthe electrode due to charging and discharging as compared with theelectrode assembly having a wound structure. That is, the electrodeassembly having a planar laminated structure is effective for anelectrode assembly using an active material that is liable to causevolume expansion.

In the embodiment shown in FIGS. 1 and 2, the positive electrodeterminal 31 and the negative electrode terminal 32 are drawn out inopposite directions, but the directions in which the positive electrodeterminal 31 and the negative electrode terminal 32 are drawn out may bearbitrary. For example, as shown in FIG. 5, the positive electrodeterminal 31 and the negative electrode terminal 32 may be drawn out fromthe same side of the electrode assembly 10. Although not shown, thepositive electrode terminal 31 and the negative electrode terminal 32may also be drawn out from two adjacent sides of the electrode assembly10. In both of the above case, the positive electrode tab 10 a and thenegative electrode tab 10 b can be formed at positions corresponding tothe direction in which the positive electrode terminal 31 and thenegative electrode terminal 32 are drawn out.

Furthermore, in the illustrated embodiment, the electrode assembly 10having a laminated structure having a plurality of positive electrodes11 and a plurality of negative electrodes 12 is shown. However, theelectrode assembly having the winding structure may have one positiveelectrode 11 and one negative electrode 12.

Hereinafter, elements constituting the electrode assembly 10 and theelectrolytic solution will be described in detail. In the followingdescription, although not particularly limited, elements in the lithiumion secondary battery will be described.

[1] Negative Electrode

The negative electrode has a structure in which, for example, a negativeelectrode active material is adhered to a negative electrode currentcollector by a negative electrode binder, and the negative electrodeactive material is laminated on the negative electrode current collectoras a negative electrode active material layer. Any material capable ofabsorbing and desorbing lithium ions with charge and discharge can beused as the negative electrode active material in the present embodimentas long as the effect of the present invention is not significantlyimpaired. Normally, as in the case of the positive electrode, thenegative electrode is also configured by providing the negativeelectrode active material layer on the current collector. Similarly tothe positive electrode, the negative electrode may also have otherlayers as appropriate.

The negative electrode active material is not particularly limited aslong as it is a material capable of absorbing and desorbing lithiumions, and a known negative electrode active material can be arbitrarilyused. For example, it is preferable to use carbonaceous materials suchas coke, acetylene black, mesophase microbead, graphite and the like;lithium metal; lithium alloy such as lithium-silicon, lithium-tin;lithium titanate and the like as the negative electrode active material.Among these, carbonaceous materials are most preferably used from theviewpoint of good cycle characteristics and safety and further excellentcontinuous charge characteristics. One negative electrode activematerial may be used alone, or two or more negative electrode activematerials may be used in combination in any combination and ratio.

Furthermore, the particle diameter of the negative electrode activematerial is arbitrary as long as the effect of the present invention isnot significantly impaired. However, in terms of excellent batterycharacteristics such as initial efficiency, rate characteristics, cyclecharacteristics, etc., the particle diameter is usually 1 μm or more,preferably 15 μm or more, and usually about 50 μm or less, preferablyabout 30 μm or less. Furthermore, for example, it can be also used asthe carbonaceous material such as a material obtained by coating thecarbonaceous material with an organic substance such as pitch or thelike and then calcining the carbonaceous material, or a materialobtained by forming amorphous carbon on the surface using the CVD methodor the like. Examples of the organic substances used for coating includecoal tar pitch from soft pitch to hard pitch; coal heavy oil such as drydistilled liquefied oil; straight run heavy oil such as atmosphericresidual oil and vacuum residual oil, crude oil; petroleum heavy oilsuch as decomposed heavy oil (for example, ethylene heavy end) producedas a by-product upon thermal decomposition of crude oil, naphtha and thelike. A residue obtained by distilling these heavy oil at 200 to 400° C.and then pulverized to a size of 1 to 100 μm can also be used as theorganic substance. In addition, vinyl chloride resin, phenol resin,imide resin and the like can also be used as the organic substance.

In one embodiment of the present invention, the negative electrodeincludes a metal and/or a metal oxide and carbon as the negativeelectrode active material. Examples of the metal include Li, Al, Si, Pb,Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, and alloys of two ormore of these. These metals or alloys may be used as a mixture of two ormore. In addition, these metals or alloys may contain one or morenon-metal elements.

Examples of the metal oxide include silicon oxide, aluminum oxide, tinoxide, indium oxide, zinc oxide, lithium oxide, and composites of these.In the present embodiment, tin oxide or silicon oxide is preferablycontained as the negative electrode active material, and silicon oxideis more preferably contained. This is because silicon oxide isrelatively stable and hardly causes reaction with other compounds. Also,for example, 0.1 to 5 mass % of one or more elements selected fromnitrogen, boron and sulfur can be added to the metal oxide. In this way,the electrical conductivity of the metal oxide can be improved. Also,the electrical conductivity can be similarly improved by coating themetal or the metal oxide with an electroconductive material such ascarbon by vapor deposition or the like.

Examples of the carbon include graphite, amorphous carbon, diamond-likecarbon, carbon nanotube, and composites of these. Highly crystallinegraphite has high electrical conductivity and is excellent inadhesiveness with respect to a negative electrode current collector madeof a metal such as copper and voltage flatness. On the other hand, sinceamorphous carbon having a low crystallinity has a relatively smallvolume expansion, it has a high effect of alleviating the volumeexpansion of the entire negative electrode, and deterioration due tononuniformity such as crystal grain boundaries and defects hardlyoccurs.

The metal and the metal oxide have the feature that the capacity ofaccepting lithium is much larger than that of carbon. Therefore, theenergy density of the battery can be improved by using a large amount ofthe metal and the metal oxide as the negative electrode active material.In order to achieve high energy density, it is preferable that thecontent ratio of the metal and/or the metal oxide in the negativeelectrode active material is high. A larger amount of the metal and/orthe metal oxide is preferable, since it increases the capacity of thenegative electrode as a whole. The metal and/or the metal oxide ispreferably contained in the negative electrode in an amount of 0.01% bymass or more of the negative electrode active material, more preferably0.1% by mass or more, and further preferably 1% by mass or more.However, the metal and/or the metal oxide has large volume change uponabsorbing and desorbing of lithium as compared with carbon, andelectrical junction may be lost. Therefore, the amount of the metaland/or the metal oxide in the negative active material is 99% by mass orless, preferably 90% or less, more preferably 80 mass % or less. Asdescribed above, the negative electrode active material is a materialcapable of reversibly absorbing and desorbing lithium ions with chargeand discharge in the negative electrode, and does not include otherbinder and the like.

For example, the negative electrode active material layer may be formedinto a sheet electrode by roll-forming the above-described negativeelectrode active material, or may be formed into a pellet electrode bycompression molding. However, usually, as in the case of the positiveelectrode active material layer, the negative electrode active materiallayer can be formed by applying and drying an application liquid on acurrent collector, where the application liquid may be obtained byslurrying the above-described negative electrode active material, abinder, and various auxiliaries contained as necessary with a solvent.

The negative electrode binder is not particularly limited, and examplesthereof include polyvinylidene fluoride, vinylidenefluoride-hexafluoropropylene copolymer, vinylidenefluoride-tetrafluoroethylene copolymer, styrene-butadiene copolymerrubber, polytetrafluoroethylene, polypropylene, polyethylene, acrylic,polyimide, polyamide imide and the like. In addition to the above,styrene butadiene rubber (SBR) and the like can be included. When anaqueous binder such as an SBR emulsion is used, a thickener such ascarboxymethyl cellulose (CMC) can also be used. The amount of thenegative electrode binder to be used is preferably 0.5 to 20 parts bymass relative to 100 parts by mass of the negative electrode activematerial from the viewpoint of a trade-off between “sufficient bindingstrength” and “high energy”. The negative electrode binders may be mixedand used.

As the material of the negative electrode current collector, a knownmaterial can be arbitrarily used, and for example, a metal material suchas copper, nickel, stainless steel, aluminum, chromium, silver and analloy thereof is preferably used from the viewpoint of electrochemicalstability. Among them, copper is particularly preferable from theviewpoint of ease of processing and cost. It is also preferable that thenegative electrode current collector is also subjected to surfaceroughening treatment in advance. Further, the shape of the currentcollector is also arbitrary, and examples thereof include a foil shape,a flat plate shape and a mesh shape. A perforated type current collectorsuch as an expanded metal or a punching metal can also be used.

The negative electrode can be produced, for example, by forming anegative electrode active material layer containing a negative electrodeactive material and a negative electrode binder on a negative electrodecurrent collector. Examples of a method for forming the negativeelectrode active material layer include a doctor blade method, a diecoater method, a CVD method, a sputtering method, and the like. Afterforming the negative electrode active material layer in advance, a thinfilm of aluminum, nickel or an alloy thereof may be formed by a methodsuch as vapor deposition, sputtering or the like to obtain a negativeelectrode current collector.

An electroconductive auxiliary material may be added to a coating layercontaining the negative electrode active material for the purpose oflowering the impedance. Examples of the electroconductive auxiliarymaterial include flaky, sooty, fibrous carbonaceous microparticles andthe like such as graphite, carbon black, acetylene black, vapor growncarbon fiber (for example, VGCF (registered trademark) manufactured byShowa Denko K.K.), and the like.

[2] Positive Electrode

The positive electrode refers to an electrode on the high potential sidein a battery. As an example, the positive electrode includes a positiveelectrode active material capable of reversibly absorbing and desorbinglithium ions with charge and discharge, and has a structure in which apositive electrode active material is laminated on a current collectoras a positive electrode active material layer integrated with a positiveelectrode binder. In one embodiment of the present invention, thepositive electrode has a charge capacity per unit area of 3 mAh/cm² ormore, preferably 0.3.5 mAh/cm² or more. From the viewpoint of safety andthe like, the charge capacity per unit area of the positive electrode ispreferably 15 mAh/cm² or less. Here, the charge capacity per unit areais calculated from the theoretical capacity of the active material. Thatis, the charge capacity of the positive electrode per unit area iscalculated by (theoretical capacity of the positive electrode activematerial used for the positive electrode)/(area of the positiveelectrode). Note that the area of the positive electrode refers to thearea of one surface, not both surfaces of the positive electrode.

The positive electrode active material in the present embodiment is notparticularly limited as long as it is a material capable of absorbingand desorbing lithium, and can be selected from several viewpoints. Ahigh-capacity compound is preferably contained from the viewpoint ofhigh energy density. Examples of the high-capacity compound includenickel lithate (LiNiO₂) and a lithium nickel composite oxide obtained bypartially replacing Ni of nickel lithate with another metal element, anda layered lithium nickel composite oxide represented by formula (A)below is preferable.

Li_(y)Ni_((1-x))M_(x)O₂  (A)

(provided that 0≤x<1, 0<y≤1.2, and M is at least one element selectedfrom the group consisting of Co, Al, Mn, Fe, Ti, and B.)

From the viewpoint of high capacity, the Ni content is preferably high,or that is to say, x is less than 0.5 in formula (A), and morepreferably 0.4 or less. Examples of such compounds includeLi_(α)Ni_(β)Co_(γ)Mn_(δ)O₂ (0<α≤1.2, preferably 1≤α≤1.2, β+γ+δ=1, β≥0.7,and γ≤0.2) and Li_(α)Ni_(β)Co_(γ)Al_(δ)O₂ (0<α≤1.2 preferably 1≤α≤1.2,β+γ+δ=1, β≥0.6 preferably β≥0.7, γ≤0.2), and, in particular,LiNi_(β)Co_(γ)Mn_(δ)O₂ (0.75≤β≤0.85, 0.05≤γ≤0.15, 0.10≤δ≤0.20). Morespecifically, for example, LiNi_(0.8)Co_(0.05)Mn_(0.15)O₂,LiNi_(0.8)Co_(0.1)Mn_(0.1)O₂, LiNi_(0.8)Co_(0.15)Al_(0.05)O₂, andLiNi_(0.8)Co_(0.1)Al_(0.1)O₂ can be preferably used.

From the viewpoint of heat stability, it is also preferable that the Nicontent does not exceed 0.5, or that is to say, x is 0.5 or more informula (A). It is also preferable that a certain transition metal doesnot account for more than half. Examples of such compounds includeLi_(α)Ni_(β)Co_(γ)Mn_(δ)O₂ (0<α≤1.2 preferably 1≤α≤1.2, β+γ+δ=1,0.2≤β≤0.5, 0.1≤γ≤0.4, 0.1≤δ≤0.4). More specific examples includeLiNi_(0.4)Co_(0.3)Mn_(0.3)O₂ (abbreviated as NCM433),LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂, LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂ (abbreviatedas NCM523), and LiNi_(0.5)Co_(0.3)Mn_(0.2)O₂ (abbreviated as NCM532)(provided that these compounds include those in which the content ofeach transition metal is varied by about 10%).

Also, two or more compounds represented by formula (A) may be used as amixture, and, for example, it is also preferable to use NCM532 or NCM523with NCM433 in a range of 9:1 to 1:9 (2:1 as a typical example) as amixture. Moreover, a battery having a high capacity and a high heatstability can be formed by mixing a material having a high Ni content (xis 0.4 or less) with a material having a Ni content not exceeding 0.5 (xis 0.5 or more, such as NCM433) in formula (A).

Other than the above positive electrode active materials, examplesinclude lithium manganates having a layered structure or a spinelstructure, such as LiMnO₂, Li_(x)Mn₂O₄ (0<x<2), Li₂MnO₃, andLi_(x)Mn_(1.5)Ni_(0.5)O₄ (0<x<2); LiCoO₂ and those obtained by partiallyreplacing these transition metals with other metals; those having anexcess of Li based on the stoichiometric compositions of these lithiumtransition metal oxides; and those having an olivine structure such asLiFePO₄. Moreover, materials obtained by partially replacing these metaloxides with Al, Fe, P, Ti, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt,Te, Zn, La, or the like can be used as well. One of the positiveelectrode active materials described above may be used singly, or two ormore can be used in combination.

A positive electrode binder similar to the negative electrode binder canbe used. Among them, polyvinylidene fluoride or polytetrafluoroethyleneis preferable from the viewpoint of versatility and low cost, andpolyvinylidene fluoride is more preferable. The amount of the positiveelectrode binder used is preferably 2 to 15 parts by mass relative to100 parts by mass of the positive electrode active material from theviewpoint of a trade-off between “sufficient binding strength” and “highenergy”.

An electroconductive auxiliary material may be added to a coating layercontaining the positive electrode active material for the purpose oflowering the impedance. Examples of the conductive auxiliary materialinclude flaky, sooty, fibrous carbonaceous microparticles and the likesuch as graphite, carbon black, acetylene black, vapor grown carbonfiber (for example, VGCF manufactured by Showa Denko K.K.) and the like.

A positive electrode current collector similar to the negative electrodecurrent collector can be used. In particular, as the positive electrode,a current collector using aluminum, an aluminum alloy, iron, nickel,chromium, molybdenum type stainless steel is preferable.

An electroconductive auxiliary material may be added to a positiveelectrode active material layer containing the positive electrode activematerial for the purpose of lowering the impedance. Examples of theconductive auxiliary material include carbonaceous microparticles suchas graphite, carbon black and acetylene black.

[3] Insulating Layer (Material and Manufacturing Method Etc.)

The insulating layer can be formed by applying a slurry composition foran insulating layer so as to cover a part of the active material layerof the positive electrode or the negative electrode and drying andremoving a solvent. Although the insulating layer may be formed on onlyone side of the active material layer, there is an advantage that thewarpage of the electrode can be reduced by forming the insulating layeron both side (in particular, as a symmetrical structure).

A slurry for the insulating layer is a slurry composition for forming aporous insulating layer. Therefore, the “insulating layer” can also bereferred to as “porous insulating layer”. The slurry for the insulatinglayer comprises non-conductive particles and a binder (or a bindingagent) having a specific composition, and the non-conductive particles,the binder and optional components are uniformly dispersed as a solidcontent in a solvent.

It is desirable that the non-conductive particles stably exist in theuse environment of the lithium ion secondary battery and areelectrochemically stable. As the non-conductive particles, for example,various inorganic particles, organic particles and other particles canbe used. Among them, inorganic oxide particles or organic particles arepreferable, and in particular, from the viewpoint of high thermalstability of the particles, it is more preferable to use inorganic oxideparticles. Metal ions in the particles sometimes form salts near theelectrode, which may cause an increase in the internal resistance of theelectrode and a decrease in cycle characteristics of the secondarybattery. The other particles include particles to which conductivity isgiven by surface treatment of the surface of fine powder with anon-electrically conductive substance. The fine powder can be made froma conductive metal, compound and oxide such as carbon black, graphite,SnO₂, ITO and metal powder. Two or more of the above-mentioned particlesmay be used in combination as the non-conductive particles.

Examples of the inorganic particles include inorganic oxide particlessuch as aluminum oxide, silicon oxide, magnesium oxide, titanium oxide,BaTiO₂, ZrO, alumina-silica composite oxide; inorganic nitride particlessuch as aluminum nitride and boron nitride; covalent crystal particlessuch as silicone, diamond and the like; sparingly soluble ionic crystalparticles such as barium sulfate, calcium fluoride, barium fluoride andthe like; clay fine particles such as talc and montmorillonite. Theseparticles may be subjected to element substitution, surface treatment,solid solution treatment, etc., if necessary, and may be used singly orin combination of two or more kinds. Among them, inorganic oxideparticles are preferable from the viewpoints of stability in theelectrolytic solution and potential stability.

The shape of the inorganic particles is not particularly limited, andmay be spherical, needle-like, rod-like, spindle-shaped, plate-like, orthe like. From the viewpoint of effectively preventing penetration ofthe needle-shaped object, the shape of the inorganic particle may be inthe form of a plate.

By orienting the inorganic particles as described above, it isconceivable that the inorganic particles are arranged so as to overlapwith each other on a part of the flat surface, and voids (through holes)from one surface to the other surface of the porous film are formed notin a straight but in a bent shape (that is, the curvature ratio isincreased). This is presumed to prevent the lithium dendrite frompenetrating the porous film and to better suppress the occurrence of ashort circuit.

Examples of the plate-like inorganic particles preferably used includevarious commercially available products such as “SUNLOVELY” (SiO₂)manufactured by AGC Si-Tech Co., Ltd., pulverized product of “NST-B 1”(TiO₂) manufactured by Ishihara Sangyo Kaisha, Ltd., plate like bariumsulfate “H series”, “HL series” manufactured by Sakai Chemical IndustryCo., Ltd., “Micron White” (Talc) manufactured by Hayashi Kasei Co.,Ltd., “Benger” (bentonite) manufactured by Hayashi Kasei Co., Ltd.,“BMM” and “BMT” (boehmite) manufactured by Kawaii Lime Industry Co.,Ltd., “Serasur BMT-B” [alumina (Al₂O₃)] manufactured by Kawaii LimeIndustry Co., Ltd., “Serath” (alumina) manufactured by Kinsei Matec Co.,Ltd., “AKP series” (alumina) manufactured by Sumitomo Chemical Co.,Ltd., and “Hikawa Mica Z-20” (sericite) manufactured by Hikawa MiningCo., Ltd. In addition, SiO₂, Al₂O₃, and ZrO can be produced by themethod disclosed in Japanese Patent Laid-Open No. 2003-206475.

The average particle diameter of the inorganic particles is preferablyin the range of 0.005 to 10 μm, more preferably 0.1 to 5 μm,particularly preferably 0.3 to 2 μm. When the average particle size ofthe inorganic particles is in the above range, the dispersion state ofthe porous film slurry is easily controlled, so that it is easy tomanufacture a porous film having a uniform and uniform thickness. Inaddition, such average particle size provides the following advantages.The adhesion to the binder is improved, and even when the porous film iswound, it is possible to prevent the inorganic particles from peelingoff, and as a result, sufficient safety can be achieved even if theporous film is thinned. Since it is possible to suppress an increase inthe particle packing ratio in the porous film, it is possible tosuppress a decrease in ion conductivity in the porous film. Furthermore,the porous membrane can be made thin.

The average particle size of the inorganic particles can be obtained byarbitrarily selecting 50 primary particles from an SEM (scanningelectron microscope) image in an arbitrary field of view, carrying outimage analysis, and obtaining the average value of circle equivalentdiameters of each particle.

The particle diameter distribution (CV value) of the inorganic particlesis preferably 0.5 to 40%, more preferably 0.5 to 30%, particularlypreferably 0.5 to 20%. By setting the particle size distribution of theinorganic particles within the above range, a predetermined gap betweenthe non-conductive particles is maintained, so that it is possible tosuppress an increase in resistance due to the inhibition of movement oflithium. The particle size distribution (CV value) of the inorganicparticles can be determined by observing the inorganic particles with anelectron microscope, measuring the particle diameter of 200 or moreparticles, determining the average particle diameter and the standarddeviation of the particle diameter, and calculating (Standard deviationof particle diameter)/(average particle diameter). The larger the CVvalue means the larger variation in particle diameter.

When the solvent contained in the slurry for insulating layer is anon-aqueous solvent, a polymer dispersed or dissolved in a non-aqueoussolvent can be used as a binder. As the polymer dispersed or dissolvedin the non-aqueous solvent, polyvinylidene fluoride (PVdF),polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP),polytrifluoroethylene chloride (PCTFE),polyperfluoroalkoxyfluoroethylene, polyimide, polyamideimide, and thelike can be used as a binder, and it is not limited thereto.

In addition, a binder used for binding the active material layer canalso be used.

When the solvent contained in the slurry for insulating layer is anaqueous solvent (a solution using water or a mixed solvent containingwater as a main component as a dispersion medium of the binder), apolymer dispersed or dissolved in an aqueous solvent can be used as abinder. A polymer dispersed or dissolved in an aqueous solvent includes,for example, an acrylic resin. As the acrylic resin, it is preferably touse homopolymers obtained by polymerizing monomers such as acrylic acid,methacrylic acid, acrylamide, methacrylamide, 2-hydroxyethyl acrylate,2-hydroxyethyl methacrylate, methyl methacrylate, ethylhexyl acrylate,butyl acrylate. The acrylic resin may be a copolymer obtained by,polymerizing two or more of the above monomers. Further, two or more ofthe homopolymer and the copolymer may be mixed. In addition to theabove-mentioned acrylic resin, polyolefin resins such as styrenebutadiene rubber (SBR) and polyethylene (PE), polytetrafluoroethylene(PTFE), and the like can be used. These polymers can be used singly orin combination of two or more kinds. Among them, it is preferable to usean acrylic resin. The form of the binder is not particularly limited,and particles in the form of particles (powder) may be used as they are,or those prepared in a solution state or an emulsion state may be used.Two or more kinds of binders may be used in different forms.

The insulating layer may contain a material other than theabove-described inorganic filler and binder, if necessary. Examples ofsuch material include various polymer materials that can function as athickener for a slurry for the insulating layer, which will be describedlater. In particular, when an aqueous solvent is used, it is preferableto contain a polymer functioning as the thickener. As the polymerfunctioning as the thickener, carboxymethyl cellulose (CMC) or methylcellulose (MC) is preferably used.

Although not particularly limited, the ratio of the inorganic filler tothe entire insulating layer is suitably about 70 mass % or more (forexample, 70 mass % to 99 mass %), preferably 80 mass % or more (forexample, 80 mass % to 99 mass %), and particularly preferably about 90mass % to 95 mass %.

The ratio of the binder in the insulating layer is suitably about 1 to30 mass % or less, preferably 5 to 20 mass % or less. In the case ofcontaining an insulating layer-forming component other than theinorganic filler and the binder, for example, a thickener, the contentratio of the thickener is preferably about 10 mass % or less, morepreferably about 7 mass % or less. If the ratio of the binder is toosmall, strength (shape retentivity) of the insulating layer itself andadhesion to the active material layer are lowered, which may causedefects such as cracking and peeling. If the ratio of the binder is toolarge, gaps between the particles of the insulating layer becomeinsufficient, and the ion permeability in the insulating layer maydecrease in some cases.

In order to maintain ion conductivity, The porosity (void ratio) (theratio of the pore volume to the apparent volume) of the insulating layeris preferably 20% or more, more preferably 30% or more. However, if theporosity is too high, falling off or cracking of the insulating layerdue to friction or impact applied to the insulating layer occurs, theporosity is preferably 80% or less, more preferably 70% or less.

The porosity can be calculated from the ratio of the materialsconstituting the insulating layer, the true specific gravity and thecoating thickness.

(Forming of Insulating Layer)

A method of forming the insulating layer will be described. As amaterial for forming the insulating layer, a paste type material(including slurry form or ink form, the same applies below) mixed anddispersed with an inorganic filler, a binder and a solvent can be used.

A solvent used for the insulating layer slurry includes water or a mixedsolvent mainly containing water. As a solvent other than waterconstituting such a mixed solvent, one or more kinds of organic solvents(lower alcohols, lower ketones, etc.) which can be uniformly mixed withwater can be appropriately selected and used. Alternatively, it may bean organic solvent such as N-methylpyrrolidone (NMP), pyrrolidone,methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, toluene,dimethylformamide, dimethylacetamide, or a combination of two or morethereof. The content of the solvent in the slurry for the insulatinglayer is not particularly limited, and it is preferably 40 to 90 mass %,particularly preferably about 50 to 70 mass %, of the entire coatingmaterial.

The operation of mixing the inorganic filler and the binder with thesolvent can be carried out by using a suitable kneading machine such asa ball mill, a homodisper, Diaper Mill (registered trademark), Clearmix(registered trademark), Filmix (registered trademark), an ultrasonicdispersing machine.

For the operation of applying the slurry for the insulating layer,conventional general coating means can be used without restricting. Forexample, a predetermined amount of the slurry for the insulating layercan be applied by coating in a uniform thickness by means of a suitablecoating device (a gravure coater, a slit coater, a die coater, a commacoater, a dip coater, etc.).

Thereafter, the solvent in the slurry for the insulating layer may beremoved by drying the coating material by means of a suitable dryingmeans.

(Thickness)

The thickness of the insulating layer is preferably 1 μm or more and 30μm or less, and more preferably 2 μm or more and 15 μm or less.

[4] Electrolyte

As the electrolytic solution, a non-aqueous electrolytic solution thatis stable at the operating potential of the battery is preferable, butit is not particularly limited. Specific examples of the non-aqueouselectrolytic solution include an aprotic organic solvent includingcyclic carbonates such as propylene carbonate (PC), ethylene carbonate(EC), fluoroethylene carbonate (FEC), t-difluoroethylene carbonate(t-DFEC), butylene carbonate (BC), vinylene carbonate (VC), vinylethylene carbonate (VEC); chain carbonates such as allyl methylcarbonate (AMC), dimethyl carbonate (DMC), diethyl carbonate (DEC),ethyl methyl carbonate (EMC), dipropyl carbonate (DPC); propylenecarbonate derivatives; aliphatic carboxylic acid esters such as methylformate, methyl acetate, ethyl propionate and the like; cyclic esterssuch as γ-butyrolactone (GBL). The non-aqueous electrolytic solution maybe used singly or in combination of two or more. Sulfur-containingcyclic compounds such as sulfolane, fluorinated sulfolane, propanesultone, propene sultone and the like can be used as the non-aqueouselectrolytic solution.

Specific examples of supporting salts contained in the electrolyticsolution include lithium salts such as LiPF₆, LiAsF₆, LiAlCl₄, LiClO₄,LiBF₄, LiSbF₆, LiCF₈SO₃, LiC₄F₉SO₃, Li(CF₃SO₂)₂, LiN(CF₃SO₂)₂ and thelike, but are not limited. As the supporting salt, one type may be usedalone, or two kinds or more may be used in combination.

[5] Separator

When the battery has a separator, the separator is not particularlylimited, and a porous film or a nonwoven fabric made of polypropylene,polyethylene, fluororesin, polyamide, polyimide, polyester,polyphenylene sulfide or the like can be used as the separator. Inaddition, those including inorganic materials such as silica, alumina,glass and the like adhered or joined to the porous firm or the nonwovenfabric used as a base material and the inorganic materials aloneprocessed into a nonwoven fabric or a cloth can also be used as theseparator. Furthermore, a laminate of the these can be used as theseparator.

The present invention is not limited to the above described lithium ionsecondary battery and can be applied to any battery. However, since theproblem of heat often occurs in batteries with high capacity in manycases, the present invention is preferably applied to batteries withhigh capacity, particularly lithium ion secondary batteries.

Next, embodiments of method for manufacturing the electrode shown inFIG. 3 will be described. In the following description, the positiveelectrode 11 and the negative electrode 12 will be described as“electrodes” without particularly distinguishing from each other, butthe positive electrode 11 and the negative electrode differ only in thematerials, shapes, etc. to be used, and the following explanation willbe made on the positive electrode 11 and the negative electrode 12.

The electrode has a structure in which the active material layer 111 andthe insulating layer 112 are laminated in this order on the currentcollector 110 finally and the manufacturing method is not particularlylimited as long as peeling occurs between the current collector 110 andthe active material layer 111 and its peeling strength is 10 mN/mm ormore when a 90° peeling test is carried out at a peeling rate of 100mm/min. At least one of the materials of the active material layer 111,the formation condition of the active material layer 111, the materialsof the insulating layer 112 and the formation condition of theinsulating layer 112 can be determined so as to satisfy the abovepeeling conditions.

The active material layer 111 can be formed by applying an mixture foran active material layer prepared by dispersing an active material and abinder in a solvent to form a slurry and drying the applied mixture forthe active material layer. After the mixture for the active materiallayer is dried, the method may further include the step ofcompression-molding the dried mixture for the active material layer. Theinsulating layer 12 can also be formed in the same process as the activematerial layer 111. That is, the insulating layer 112 can be formed byapplying an mixture for an insulating layer prepared by dispersing aninsulating material and a binder in a solvent to form a slurry, anddrying the applied mixture for the insulating layer. After the mixturefor the insulating layer is dried, the method may further include thestep of compression molding the dried mixture for the insulating layer.

The process for forming the active material layer 111 and the processfor forming the insulating layer 112 described above may be carried outseparately or in appropriate combination. In the case where the processfor forming the active material layer 111 and the process for formingthe insulating layer 112 are separately carried out, the manufacturingmethod for the electrode includes

(1) applying a mixture for an active material on a current collector110,(2) drying the applied mixture for the active material,(3) forming an active material layer 111 by compression-molding thedried mixture for the active material mixture,(4) applying a mixture for an insulating layer on the formed activematerial layer 111,(5) drying the applied mixture for the insulating layer, and(6) forming an insulating layer 112 by compression-molding the driedmixture for the insulating layer. In this case, since the insulatinglayer 112 is formed after the active material layer 111 is formed, it ispossible to easily manage the thickness of each layer and the like. Thestep of compression-molding the mixture for the active material layerand the step of compression molding the mixture for the insulating layercan be omitted.

When combining the process of forming the active material layer 111 andthe process of forming the insulating layer 112, there are severalexamples of the combination. Two examples among them are describedbelow.

Combination Example A

In Combination Example A, the process of manufacturing the electrodeincludes

(A1) applying the mixture for the active material layer on the currentcollector 110,(A2) drying the applied mixture for the active material layer,(A3) applying a mixture for an insulating layer on the dried mixture forthe active material layer,(A4) drying the applied mixture for the insulating layer, and(A5) compression-molding the dried mixture for the active material layerand the dried mixture for the insulating layer mixture simultaneously.In this case, only one step of compression-molding is required, and themanufacturing process is simplified correspondingly. The above step ofcompression-molding can be omitted.

Combination Example B

In the combination Example B, the process of manufacturing the electrodeincludes

(B1) applying a mixture for an active material layer on the currentcollector 110,(B2) applying an mixture for an insulating layer on the applied mixturefor the active material layer,(B3) drying the whole of the applied mixture for the active materiallayer and the applied mixture for the insulating layer simultaneously,and(B4) compression-molding the whole of the dried mixture for the activematerial layer and the mixture for the insulating layer simultaneously.In this case, since only one step of drying and one step ofcompression-molding are required, the manufacturing process is furthersimplified. The above step of compression-molding can be omitted.

For manufacturing the electrode, for example, the manufacturingapparatus shown in FIG. 6 can be used. The manufacturing apparatus shownin FIG. 6 includes a backup roller 201, a die coater 210 and a dryingmachine 203.

The backup roller 201 rotates in a state in which the long currentcollector 110 is wound on the outer peripheral surface of the backuproller 201 whereby the current collector 110 is fed in the rotationdirection of the backup roller 201 while the rear surface of the currentcollector 110 is supported. The die coater 210 has a first die head 211and a second die head 212 which are spaced from each other in the radialdirection and the circumferential direction of the backup roller 201with respect to the outer circumferential surface of the backup roller201.

The first die head 211 is for applying the active material layer 111 onthe surface of the current collector 110 and is located on the upstreamside of the second die head 212 with respect to the feed direction ofthe current collector 110. A discharge opening 211 a having a widthcorresponding to the applying width of the active material layer 111 isopened at the tip of the first die head 211 facing the backup roller201. The slurry for the active material layer is discharged from thedischarger opening 211 a. The slurry for the active material layer isprepared by dispersing particles of an active material and a binder(binding agent) in a solvent, and is supplied to the first die head 211.

The second die head 212 is for applying the insulating layer 112 on thesurface of the active material layer 111 and is located on thedownstream side of the first die head 211 with respect to the feeddirection of the current collector 110. A discharge opening 212 a havinga width corresponding to the applying width of the insulating layer 112is opened at the tip of the second die head 212 facing the backup roller201. The slurry for the insulating layer is discharged from thedischarge opening 212 a. The slurry for the insulating layer is preparedby dispersing insulating particles and a binder (binding agent) in asolvent, and is supplied to the second die head 212.

A solvent is used for preparing the slurry for the active material layerand the slurry for the insulating layer. When N-methyl-2-pyrrolidone(NMP) is used as the solvent, peeling strength of the layer obtained byevaporating the solvent can be increased compared with the case of usingan aqueous solvent. When N-methyl-2-pyrrolidone was used as a solvent,the solvent did not evaporate completely even if the solvent wasevaporated in a subsequent step, and the obtained layer contains aslight amount of N-methyl-2-pyrrolidone.

The drying machine 203 is for evaporating the solvent from the slurryfor the active material layer and the slurry for the insulating layerrespectively discharged from the first die head 211 and the second diehead 212. The slurries are dried by the evaporation of the solvent,whereby the active material layer 111 and an insulating layer 112 areformed.

Next, a manufacturing process of the electrode by means of themanufacturing apparatus shown in FIG. 6 will be described. Forconvenience of explanation, the slurry for the active material layer andthe active material layer obtained therefrom are described as “activematerial layer 111” without distinguishing between them. Actually, the“active material layer 111” before drying means the slurry for theactive material layer. Similarly, the “insulating layer 112” beforedrying means the slurry for the insulating layer.

First, the active material layer 111 slurried with a solvent isintermittently applied to the surface of the long current collector 110supported and fed on the backup roller 201 by using the first die head211. As a result, as shown in FIG. 6A, a slurry of the active materiallayer 111 is applied to the current collector 110 at intervals in thefeeding direction A of the current collector 110. By intermittentlyapplying the active material layer 111 with the first die head 211, theactive material layer 111 is applied in a rectangular shape having alongitudinal length parallel to the feeding direction A of the currentcollector 110 and a lateral length along a direction orthogonal thereto.

Next, when the leading end of the applied active material layer 111 inthe feeding direction of the current collector 111 is fed to a positionfacing the discharge opening 212 a of the second die head 212, theinsulating layer 112 slurried with solvent is intermittently applied tothe active material layer 111 by using the second die head 212. Theinsulating layer 112 is applied so that a part thereof is exposed at theend portion of the active material layer 111 when viewing the currentcollector 110 in its thickness direction. The insulating layer 112 isapplied before the active material layer 111 is dried, that is, beforethe solvent of the active material layer 111 is evaporated. Byintermittently applying the insulating layer 112 with the second diehead 212, the insulating layer 112 is applied in a rectangular shapehaving a longitudinal length parallel to the feeding direction A of thecurrent collector 110 and a lateral length along a directionperpendicular thereto.

In the present embodiment, the first die head 211 and the second diehead 212 have the same width (the dimension in the direction orthogonalto the feeding direction A of the current collector 110) of theprojecting openings 211 a and 212 a, and the active material layer 111and the insulating layer 112 have the same applying width.

After applying the active material layer 111 and the insulating layer112, the current collector 110 is fed to the drying machine 203, thesolvents of the slurry for the active material layer and the slurry forthe insulating layer slurry are evaporated in the drying machine 203.After evaporation of the solvent, the current collector 110 is fed to aroll press where the active material layer 111 and the insulating layer112 are compression-molded. Thus, the active material layer 111 isformed simultaneously with the formation of the insulating layer 112.

Finally, the current collector 110 is cut into a desired shape, asindicated by a broken line in FIG. 6C, having a rectangular portion inwhich the active material layer 111 and the insulating layer 112 areformed on the entire surface of the current collector 110 and anextension portion 110 a made of the current collector 110 extending fromthe rectangular portion by an appropriate method such as punching. Theelectrode is thereby obtained. The cutting step may be carried out so asto obtain a desired shape by one time of processing or it may be carriedout so as to obtain a desired shape by a plurality of times ofprocessing.

Note that the current collector 110 having the active material layer 111and the insulating layer 112 formed thereon is often wound around a rolland stored and/or transported until the next process. As describedabove, in the laminated structure of the current collector 110, theactive material layer 111, and the insulating layer 112, peeling occursbetween the current collector 110 and the active material layer 111 andits peeling strength is 10 mN/mm or more when the 90° peeling test iscarried out. Therefore, it is possible to suppress peeling of the activematerial layer 111 from the current collector 110 and peeling of theinsulating layer 112 from the active material layer 111 even when woundon a roll.

Although the present invention has been described with reference to oneembodiment, the present invention is not limited to the above-describedembodiments, and can be arbitrarily changed within the scope of thetechnical idea of the present invention.

For example, in the above embodiment, in order to apply the activematerial layer 111 and the insulating layer 112, a die coater 210 havingtwo die heads 211 and 212 with discharge openings 211 a and 212 a asshown in FIG. 6 was used. However, as shown in FIG. 7, the activematerial layer 111 and the insulating layer 112 can be applied to thecurrent collector 110 by using a die coater 220 having a single die head221 with two discharge openings 221 a and 221 b.

The two discharge openings 221 a and 221 b are arranged at intervals inthe rotation direction of the backup roller 201, that is, the feeddirection of the current collector 110. The slurry for the activematerial layer is applied by the discharge opening 221 a located on theupstream side in the feed direction of the current collector 110 and theslurry for the insulating layer is applied by the discharge opening 221b located on the downstream side. Therefore, the slurry for the activematerial layer and the slurry for the insulating layer are dischargedrespectively from the two discharge openings 221 a and 221 b, thereby itis possible to obtain a structure that the active material layer 111 isintermittently applied to the surface of the current collector 110 andthe insulating layer 112 is applied with a part of the active materiallayer 111 exposed.

Furthermore, in the above embodiment, the case where the active materiallayer 111 and the insulating layer 112 are applied to one side of thecurrent collector 110 has been described. However, it is possible tomanufacture an electrode having the active material layer 111 and theinsulating layer 112 on both surface of the current collector 110 byapplying the active material layer 111 and the insulating layer 112 onthe other side of the current collector 110 in a similar manner.

Further, the battery obtained by the present invention can be used invarious uses. Some examples are described below.

[Battery Pack]

A plurality of batteries can be combined to form a battery pack. Forexample, the battery pack may have a configuration in which two or morebatteries according to the present embodiment are connected in seriesand/or in parallel. The series number and parallel number of thebatteries can be appropriately selected according to the intendedvoltage and capacity of the battery pack.

[Vehicle]

The above-described battery or the battery pack thereof can be used fora vehicle. Examples of vehicles that can use batteries or assembledbatteries include hybrid vehicles, fuel cell vehicles, and electricvehicles (four-wheel vehicles (commercial vehicles such as passengercars, trucks and buses, and mini-vehicles, etc.), motorcycles (motorbikeand tricycles). Note that the vehicle according to the presentembodiment is not limited to an automobile, and the battery can also beused as various power sources for other vehicles, for example,transportations such as electric trains. As an example of such avehicle, FIG. 8 shows a schematic diagram of an electric vehicle. Theelectric vehicle 200 shown in FIG. 8 has a battery pack 210 configuredto satisfy the required voltage and capacity by connecting a pluralityof the above-described batteries in series and in parallel.

[Power Storage Device]

The above-described battery or the battery pack thereof can be used fora power storage device. Examples of the power storage device using thesecondary battery or the battery pack thereof include a power storagedevice which is connected between a commercial power supply supplied toan ordinary household and a load such as a household electric applianceto use as a backup power source or an auxiliary power source in case ofpower outage, and a power storage device used for large-scale electricpower storage for stabilizing electric power output with large timevariation due to renewable energy such as photovoltaic power generation.An example of such a power storage device is schematically shown in FIG.9. The power storage device 300 shown in FIG. 9 has a battery pack 310configured to satisfy a required voltage and capacity by connecting aplurality of the above-described batteries in series and in parallel.

[Others]

Furthermore, the above-described battery or the battery pack thereof canbe used as a power source of a mobile device such as a mobile phone, anotebook computer and the like.

The present invention will be described with reference to specificexamples below. However, the present invention is not limited to thefollowing examples.

Example 1 (Preparation of Insulating Applied Positive Electrode)

LiNi_(0.8)Mn_(0.15)Co_(0.05), a carbon conductive agent (acetyleneblack) and polyvinylidene fluoride (PVdF) as a binder were dispersed inN-methyl-2-pyrrolidone at a weight ratio of 90:5:5 to prepare a slurryfor a positive electrode active material layer. This slurry was appliedto the surface of a positive electrode current collector foil made ofaluminum and dried to form a positive electrode active material layer(PAM 1). A positive electrode active material layer was similarly formedon the back surface of the positive electrode current collector foil.

Subsequently, alumina and polyvinylidene fluoride (PVdF) as a binderwere dispersed in N-methyl-2-pyrrolidone at a weight ratio of 90:10 toprepare a slurry for an insulating layer. This was applied to thepositive electrode active material layer and dried to form an insulatinglayer (INS 1). An insulating layer was similarly formed on the positiveelectrode active material layer on the back side of the positiveelectrode current collector foil. Subsequently, the whole of thepositive electrode current collector foil, the positive electrode activematerial layer and the insulating layer were compression-molded andfurther cut into a predetermined shape to prepare a plurality ofpositive electrodes.

(Measurement of Peeling Strength)

One of the obtained plurality of positive electrodes was cut out as asample having a width of 20 mm and a length of 100 mm, and 90° peelingtest was carried out using this sample under an ambient temperatureenvironment (15° C. to 25° C.). The 90° peeling test was carried out asfollows. First, the sample was fixed on the upper surface of a flatsample stage using a double-sided tape (NWBB-20 manufactured by NichibanCo., Ltd.) having the same width as the sample so that the double-sidedtape was not peeled off. At that time, only the portion of the samplefrom the one end to 80 mm in the length direction was fixed to thesample stage, and the remaining portion of 20 mm length was not fixed asa clamping margin. Next, the clamping margin of the sample was held by achuck, and in that state, the chuck was moved at a speed of 100 mm/minin a direction away from the sample stage perpendicular to the uppersurface of the sample stage, the sample was peeled off from the samplestage, and the maximum load at that time was measured. For 90° peelingtest, a tensile and compression tester (model number FGS-20TV,manufactured by Nidec Shimpo Co., Ltd.) was used. In the 90° peelingtest, the peeling strength and layer and location where peel wasoccurred was determined. The peeling strength is a value converted intoa force per 1 mm width of a sample by dividing the maximum load measuredwhen the sample is peeled as described above by 20 mm which is the widthof the sample. The unit of the peeling strength is expressed in Nm/mm.

(Preparation of Negative Electrode)

Natural graphite, sodium carboxymethyl methyl cellulose as a thickenerand styrene butadiene rubber as a binder were mixed in an aqueoussolution at a weight ratio of 97:1:2 to prepare a slurry for a negativeelectrode active material layer. This was applied to the surface of anegative electrode current collector foil made of copper and dried toform a negative electrode active material layer (NAM 1). A negativeelectrode active material layer was similarly formed on the back surfaceof the negative electrode current collector foil. Subsequently, thewhole of negative electrode current collector foil and the negativeelectrode active material layer were compression-molded and further cutinto a predetermined shape to prepare a plurality of negativeelectrodes.

(Preparation of Electrolytic Solution)

For a non-aqueous solvent of the electrolytic solution, a non-aqueoussolvent obtained by mixing ethylene carbonate (EC) and diethyl carbonate(DEC) in a volume ratio of 30:70 was used. As a supporting salt, LiPF₆was dissolved so as to have a concentration of 1 M.

(Preparation of Battery)

The positive electrode and the negative electrode were laminated via thebase of the separator to prepare an electrode assembly. As theseparator, a microporous separator made of polypropylene and having athickness of 25 μm was used. The size of the electrode assembly wasadjusted so that the initial charge capacity of the cell was 1 Ah.Terminals for taking out current were connected to each of the laminatedpositive electrode and negative electrode, and they were accommodated ina casing package which is a laminated film of aluminum and resin. Afterinjecting the electrolytic solution into the casing, the casing wassealed under reduced pressure. A battery was prepared by the abovesteps.

(160° C. Heating Test)

After the prepared battery was charged to 4.2 V, heating test at 160° C.was carried out. The heating rate was 10° C./min, and the temperaturewas maintained for 30 minutes after reaching 160° C.

Example 2

A positive electrode having an insulating layer was prepared in the samemanner as Example 1 expect that the positive electrode active materialwas changed from LiNi_(0.8)Mn_(0.15)Co_(0.05) that was used in Example 1to LiNi_(0.8)Ta_(0.15)Al_(0.05) and that a positive active materiallayer (PAM 2) was formed using this positive active material. Further, abattery was prepared in the same manner as Example 1 except that theabove positive electrode was used. The peeling test of the preparedpositive electrode and the 160° C. heating test of the prepared batterywere carried out in the same manner as Example 1.

Example 3

A positive electrode having an insulating layer was prepared in the samemanner as Example 1 except that the positive electrode active materialwas changed from LiNi_(0.8)Mn_(0.15)Co_(0.05) that was used in Example 1to LiNi_(0.5)Mn_(0.3)Co_(0.2) and that a positive electrode activematerial layer (PAM 3) was formed using this positive electrode activematerial. Further, a battery was prepared in the same manner as Example1 except that this positive electrode was used. The peeling test of theprepared positive electrode and the 160° C. heating test of the preparedbattery were carried out in the same manner as Example 1.

Example 4 (Preparation of Insulation Coated Negative Electrode)

Graphite, sodium carboxymethyl methyl cellulose as a thickener andstyrene butadiene rubber as a binder were mixed in an aqueous solutionat a weight ratio of 97:1:2 to prepare a slurry for a negative electrodeactive material layer. The slurry was applied to the surface of anegative electrode current collector foil made of copper and dried toform a negative electrode active material layer (NAM 1). A negativeelectrode active material layer was similarly formed on the back surfaceof the negative electrode current collector foil. Subsequently, thenegative electrode active material layers formed on both sides of thenegative electrode current collector foil were compression-molded.

Subsequently, alumina and polyvinylidene fluoride (PVdF) as a binderwere dispersed in N-methyl-2-pyrrolidone at a weight ratio of 90:10 toprepare a slurry for an insulating layer. This slurry was applied to thenegative electrode active material layer and dried to form an insulatinglayer (INS 1). An insulating layer was similarly formed on the negativeelectrode active material layer on the back side of the negativeelectrode current collector foil. Next, the insulating layers formed onboth sides of the negative electrode current collector foil werecompression-molded and further cut into a predetermined shape to preparea plurality of negative electrodes. For the prepared negative electrode,the peeling test was carried out in the same manner as Example 1.

(Preparation of Positive Electrode)

LiNi_(0.8)Mn_(0.15)Co_(0.05), a carbon conductive agent (acetyleneblack) and polyvinylidene fluoride (PVdF) as a binder were dispersed inN-methyl-2-pyrrolidone at a weight ratio of 90:5:5 to prepare a slurryfor a positive electrode active material layer. This slurry was appliedto the surface of a positive electrode current collector foil made ofaluminum and dried to form a positive electrode active material layer(PAM 1). A positive electrode active material layer was similarly formedon the back surface of the positive electrode current collector foil.Subsequently, the whole of the positive electrode current collector foiland the positive electrode active material layer was compression-moldedand further cut into a predetermined shape to prepare a plurality ofpositive electrodes.

(Preparation of Battery)

After preparation of the negative electrode and the positive electrode,an electrolytic solution and a battery were prepared in the same manneras Example 1. Using the prepared battery, the 160° C. heating test wascarried out under the same conditions as Example 1.

Example 5

Graphite and polyacrylic acid as a binder were mixed in an aqueoussolution at a weight ratio of 95:5 to prepare a slurry for a negativeelectrode active material layer. A negative electrode was prepared inthe same manner as Example 4 except that the negative electrode activematerial layer (NAM 2) was formed using this slurry, and the peelingtest of the negative electrode was carried out. In addition, a batterywas prepared in the same manner as Example 4 except that the abovenegative electrode was used, and the 160° C. heating test was carriedout.

Example 6

Graphite, Si and polyacrylic acid as a binder were mixed in an aqueoussolution at a weight ratio of 92:3:5 to prepare a slurry for a negativeelectrode active material layer. A negative electrode was prepared inthe same manner as Example 4 except that the negative electrode activematerial layer (NAM 3) was formed using this slurry, and the peelingtest was carried out. In addition, a battery was prepared in the samemanner as Example 4 except that the above negative electrode was used,and the 160° C. heating test was carried out.

Example 7

Alumina and polyacrylic acid (PAA) as a binder were mixed in an aqueoussolution at a weight ratio of 93:7 to prepare a slurry for an insulatinglayer. A negative electrode was prepared in the same manner as Example 4except that the negative electrode insulating layer (INS 2) was formedusing this slurry, and the peeling test was carried out. In addition, abattery was prepared in the same manner as Example 4 except that theabove negative electrode was used, and the 160° C. heating test wascarried out.

Example 8

Graphite and polyvinylidene fluoride (PVdF) as a binder were dispersedin N-methyl-2-pyrrolidone at a weight ratio of 95:5 to prepare a slurryfor a negative electrode active material. This slurry was applied to thesurface of a negative electrode current collector foil made of copperand dried to form a negative electrode active material layer (NAM 4). Anegative electrode active material layer was similarly formed on theback surface of the negative electrode current collector foil.

Subsequently, alumina and polyimide as a binder were dispersed inN-methyl-2-pyrrolidone at a weight ratio of 90:10 to prepare a slurryfor an insulating layer. This slurry was applied to the negativeelectrode active material layer and dried to form an insulating layer(INS 3). An insulating layer was similarly formed on the negativeelectrode active material layer on the back side of the negativeelectrode current collector foil. Next, the whole of the negativeelectrode current collector foil, the negative electrode active materiallayer and the insulating layer were compression-molded and further cutinto a predetermined shape to prepare a plurality of negativeelectrodes. For the prepared negative electrode, the peeling test wascarried out in the same manner as Example 4. In addition, a battery wasprepared in the same manner as in Example 4 except that the abovenegative electrode was used, and the 160° C. heating test was carriedout.

Example 9

Graphite, SiO and polyacrylic acid as a binder were mixed in an aqueoussolution at a weight ratio of 28:67:5 to prepare a slurry for a negativeelectrode active material layer. A negative electrode was prepared inthe same manner as Example 4 except that the negative electrode activematerial layer (NAM 4) was formed using this slurry, and the peelingtest was carried out. In addition, a battery was prepared in the samemanner as Example 4 except that the above negative electrode was used,and the 160° C. hearing test was carried out.

Comparative Example 1

Graphite, sodium carboxymethyl methyl cellulose as a thickener, andstyrene butadiene rubber as a binder were mixed in an aqueous solutionat a weight ratio of 97.6:1.2:1.2 to prepare a slurry for a negativeelectrode active material layer. A negative electrode was prepared inthe same manner as Example 4 except that the negative electrode activematerial layer (NAM 5) was formed using this slurry, and the peelingtest of the negative electrode was carried out. In addition, a batterywas prepared in the same manner as Example 4 except that the abovenegative electrode was used, and the 160° C. heating test was carriedout.

Comparative Example 2

Alumina and polyvinylidene fluoride (PVdF) as a binder were dispersed inN-methyl-2-pyrrolidone at a weight ratio of 97:3 to prepare a slurry foran insulating layer. A positive electrode was prepared in the samemanner as Example 1 except that the insulating layer (INS 4) of thepositive electrode was formed using this slurry, and the peeling testwas carried out. In addition, a battery was prepared in the same manneras Example 1 except that the above positive electrode was used, and the160° C. heating test was carried out.

Comparative Example 3

A positive electrode was prepared in the same manner as Example 1 exceptthat an insulating layer (INS 5) for a positive electrode was formed byusing a slurry for the insulating layer in which alumina andpolyvinylidene fluoride (PVdF) as a binder were dispersed inN-methyl-2-pyrrolidone at a weight ratio of 92:8, and that a dryingprocess and a compression-molding process ware added after a slurry fora positive electrode active material layer was applied to both surfacesof the positive electrode current collector foil The peeling test wascarried out on the prepared positive electrode. In addition, a batterywas prepared in the same manner as Example 1 except that the abovepositive electrode was used, and the 160° C. heating test was carriedout.

Table 1 shows the layer configurations of the positive electrode and thenegative electrode, the results of the peeling test and the results ofthe 160° C. heating test of Examples 1 to 8 and Comparative Examples 1to 3.

TABLE 1 Electrode having insulating layer Applying Peeling PositiveNegative Insulation Peeled Strength 160° C. Electrode Electrode LayerPortion (mN/mm) Heating Test Example 1 Al/CAM1/INS1 Cu/NAM1 beforeCCF-AML 21 No smoking/ compression firing Example 2 Al/CAM2/INS1 Cu/NAM1before CCF-AML 18 No smoking/ compression firing Example 3 Al/CAM3/INS1Cu/NAM1 before CCF-AML 20 No smoking/ compression firing Example 4Al/CAM1 Cu/NAM1/INS1 after CCF-AML 15 No smoking/ compression firingExample 5 Al/CAM1 Cu/NAM2/INS1 after CCF-AML 12 No smoking/ compressionfiring Example 6 Al/CAM1 Cu/NAM3/INS1 after CCF-AML 11 No smoking/compression firing Example 7 Al/CAM1 Cu/NAM1/INS2 after CCF-AML 15 Nosmoking/ compression firing Example 8 Al/CAM1 Cu/NAM4/INS3 beforeCCF-AML 30 No smoking/ compression firing Example 9 Al/CAM1 Cu/NAM4/INS1After CCF-AML 35 No smoking/ compression firing Comparative Al/CAM1Cu/NAM5/INS1 after CCF-AML 9.2 Smoking Example 1 compression ComparativeAl/CAM1/INS4 Cu/NAM1 before AML-IL 10 Smoking Example 2 compressionComparative Al/CAM1/INS5 Cu/NAM1 after AML-IL 12 Smoking Example 3compression

In Table 1, the column of the positive electrode represents the materialof “positive electrode current collector foil/positive electrode activematerial layer/insulating layer”. Similarly, the column of the negativeelectrode represents the material of “negative electrode currentcollector foil/negative electrode active material layer/insulatinglayer”. The details of PAM 1 to PAM 3, NAM 1 to NAM 5 and INS 1 to INS 5are as described in the above-mentioned Examples 1 to 9 and ComparativeExamples 1 to 3.

In each of Examples 1 to 9, peeling occurred between the currentcollector foil and the active material layer in the peel test, and thepeeling strength thereof was 10 mN/mm or more. Furthermore, smoking andfiring from the battery were not confirmed in the 160° C. heating test.On the other hand, in Comparative Examples 2 and 3, although the peelingstrength was 10 mN/mm or more, peeling occurred between the activematerial layer and the insulating layer, and smoke was generated fromthe battery in the 160° C. heating test. In Comparative Example 1,peeling occurred between the current collector foil and the activematerial layer as in Examples 1 to 8, but the peeling strength wasrelatively small as 9.2 mN/mm, and smoking was generated in the heatingtest. From the above, it was found that smoking and heat generation canbe effectively suppressed even though the temperature of the battery ishigh by configuring the electrode having the insulating layer further onthe active material layer such that peeling occurs between the currentcollector foil and the active material layer and its peeling strength is10 mN/mm or more when 90° peeling test was carried out.

Here, in the Comparative Examples 2 and 3, a mechanism in which smokewas generated in the heating test will be considered. In ComparativeExamples 2 and 3, peeling occurred between the active material layer andthe insulating layer, which means that the adhesion force between theactive material layer and the insulating layer is lower than theadhesion force between active material layer and the current collectingfoil. In the heating test, the positive electrode, the negativeelectrode and the separator are heated, and a shrinking force in thein-plane direction is exerted on the separator by heating. At the sametime, contracting force acts also on the positive electrode and thenegative electrode that are in contact with the separator so as to bepulled by the separator. By this contracting force, in the negativeelectrode, the insulating layer is peeled from the active material layerso as to be pulled by the separator and the active material layer ispartially exposed. As a result, it is considered that a short circuitoccurred between the positive electrode and the negative electrode,resulting in smoking.

Some or all of the above embodiments may also be described as follows,but the disclosure of the present application is not limited to thefollowing further exemplary embodiments.

Further Exemplary Embodiment 1

An electrode for a battery comprising:

a current collector (110),

an active material layer (111) formed on at least one surface of thecurrent collector (110),

an insulating layer (112) formed on a surface of the active materiallayer (111), and

wherein peeling occurs between the current collector (110) and theactive material layer (111) and a peeling strength thereof is 10 mN/mmor more when a 90° peeling test is carried out at a peeling rate of 100mm/min.

Further Exemplary Embodiment 2

The electrode according to Further exemplary embodiment 1, wherein thecurrent collector (110) and the active material layer (111) are thecurrent collector (110) for a positive electrode.

Further Exemplary Embodiment 3

The electrode according to Further exemplary embodiment 2, wherein theactive material layer (111) for the positive electrode includespolyvinylidene fluoride as a binder.

Further Exemplary Embodiment 4

The electrode according to Further exemplary embodiment 1, wherein thecurrent collector (110) and the active material layer (111) are thecurrent collector (110) and the active material layer (111) for anegative electrode.

Further Exemplary Embodiment 5

The electrode according to Further exemplary embodiment 4, wherein theactive material layer (111) for the negative electrode includes at leastone of styrene butadiene rubber, polyacrylic acid and polyvinylidenefluoride as a binder.

Further Exemplary Embodiment 6

The electrode according to any one of Further exemplary embodiments 1 to5, wherein the active material layer (111) includesN-methyl-2-pyrrolidone.

Further Exemplary Embodiment 7

A battery comprising:

at least one positive electrode (11),

at least one negative electrode (12) disposed to face the positiveelectrode (11), and

wherein at least one of the positive electrode (11) and the negativeelectrode (12) includes a current collector (110), an active materiallayer (111) formed on at least one surface of the current collector(110), and an insulating layer (112) formed on a surface of the activematerial layer (111), and peeling occurs between the current collector(110) and the active material layer (111) and a peeling strength thereofis 10 mN/mm or more when a 90° peeling test is carried out at a peelingrate of 100 mm/min.

Further Exemplary Embodiment 8

The battery according to Further exemplary embodiment 7, wherein thepositive electrode (11) and the negative electrode (12) are disposed toface each other with the insulating layer (112) interposed therebetween.

Further Exemplary Embodiment 9

The battery according to Further exemplary embodiment 7 or 8, furthercomprising a separator (13) disposed between the positive electrode (11)and the negative electrode (12).

Further Exemplary Embodiment 10

The battery according to any one of Further exemplary embodiments 7 to9, wherein the active material layer (111) includes polyvinylidenefluoride as a binder.

Further Exemplary Embodiment 11

The battery according to any one of Further exemplary embodiments 7 to10, wherein the active material layer (111) includesN-methyl-2-pyrrolidone.

Further Exemplary Embodiment 12

A method for manufacturing an electrode for a battery, the methodcomprising;

forming an active material layer (111) on at least one surface of acurrent collector (110),

forming an insulating layer (112) such that the insulating layer (112)is finally laminated on a surface of the active material layer (111),and

wherein at least one of a material of the active material layer (111), aformation condition of the active material layer (111), a material ofthe insulating layer (112) and a formation condition of the insulatinglayer (112) is determined such that peeling occurs between the currentcollector (110) and the active material layer (111) and a peelingstrength thereof is 10 mN/mm or more when a 90° peeling test is carriedout at a peeling rate of 100 mm/min.

Further Exemplary Embodiment 13

The method for manufacturing the electrode according to Furtherexemplary embodiment 12,

wherein the step of forming the active material layer (111) comprises:

applying a mixture for the active material layer in which an activematerial and a binder are dispersed in a solvent,

drying the mixture for the active material layer after the mixture isapplied, and

compression-molding the mixture for the active material layer after themixture is dried, and

wherein the step of forming the insulating layer (112) comprises:

applying a mixture for the insulating layer in which an insulatingmaterial and a binder are dispersed in a solvent,

drying the mixture for the insulating layer after the mixture isapplied, and

compression-molding the mixture for the insulating layer after themixture is dried.

Further Exemplary Embodiment 14

The method for manufacturing the electrode according to Furtherexemplary embodiment 13,

wherein the step of applying the mixture for the active material layer,

the step of drying the mixture for the active material layer,

the step of compression-molding the mixture for the active materiallayer,

the step of applying the mixture for the insulating layer,

the step of drying the mixture for the insulating layer and

the step of compression-molding the mixture for the insulating layer

are carried out in this order.

Further Exemplary Embodiment 15

The method for manufacturing the electrode according to Furtherexemplary embodiment 13,

wherein the step of applying the mixture for the active material layer,

the step of drying the mixture for the active material layer,

the step of applying the mixture for the insulating layer and

the step of drying the mixture for the insulating layer

are carried out in this order, and

wherein the step of compression-molding the mixture for the activematerial layer and the step of compression-molding the mixture for theinsulating layer are carried out simultaneously after the step of dryingthe mixture for the insulating layer.

Further Exemplary Embodiment 16

The method for manufacturing the electrode according to Furtherexemplary embodiment 13,

wherein the step of applying the mixture for the active material layerand

the step of applying the mixture for the insulating layer

are carried out in this order,

the step of drying the mixture for the active material layer and thestep of drying the mixture for the insulating layer are carried outsimultaneously after the step of applying the mixture for the insulatinglayer, and

the step of compression-molding the mixture for the active materiallayer and the step of compression-molding the mixture for the insulatinglayer are carried out simultaneously thereafter.

Further Exemplary Embodiment 17

The method for manufacturing the electrode according to any one ofFurther exemplary embodiments 13 to 16, wherein the mixture for theactive material layer includes polyvinylidene fluoride as the binder.

Further Exemplary Embodiment 18

The method for manufacturing the electrode according to any one ofFurther exemplary embodiments 13 to 17, wherein the mixture for theactive material layer includes N-methyl-2-pyrrolidone as the solvent.

EXPLANATION OF SYMBOLS

-   1 Battery-   10 Electrode assembly-   10 a Positive electrode tab-   10 b Negative electrode tab-   11 Positive electrode-   12 Negative electrode-   13 Separator-   21, 22 Casing member-   31 Positive electrode terminal-   32 Negative electrode terminal-   110 Current collector-   110 a Extended portion-   111 Active material layer-   112 Insulating layer-   201 Backup roller-   210, 220 Die coater-   211, 212, 221 Die head-   211 a, 212 a, 221 a Discharge opening

1. An electrode for a battery comprising: a current collector, an activematerial layer formed on at least one surface of the current collector,an insulating layer formed on a surface of the active material layer,and wherein peeling occurs between the current collector and the activematerial layer and a peeling strength thereof is 10 mN/mm or more when a90° peeling test is carried out at a peeling rate of 100 mm/min.
 2. Theelectrode according to claim 1, wherein the current collector and theactive material layer are the current collector for a positiveelectrode.
 3. The electrode according to claim 2, wherein the activematerial layer for the positive electrode includes polyvinylidenefluoride as a binder.
 4. The electrode according to claim 1, wherein thecurrent collector and the active material layer are the currentcollector and the active material layer for a negative electrode.
 5. Theelectrode according to claim 4, wherein the active material layer forthe negative electrode includes at least one of styrene butadienerubber, polyacrylic acid and polyvinylidene fluoride as a binder.
 6. Theelectrode according to claim 1, wherein the active material layerincludes N-methyl-2-pyrrolidone.
 7. A battery comprising: at least onepositive electrode, at least one negative electrode disposed to face thepositive electrode, and wherein at least one of the positive electrodeand the negative electrode includes a current collector, an activematerial layer formed on at least one surface of the current collector,and an insulating layer formed on a surface of the active materiallayer, and peeling occurs between the current collector and the activematerial layer and a peeling strength thereof is 10 mN/mm or more when a90° peeling test is carried out at a peeling rate of 100 mm/min.
 8. Thebattery according to claim 7, wherein the positive electrode and thenegative electrode are disposed to face each other with the insulatinglayer interposed therebetween.
 9. The battery according to claim 7,further comprising a separator disposed between the positive electrodeand the negative electrode.
 10. The battery according to claim 7,wherein the active material layer includes polyvinylidene fluoride as abinder.
 11. The battery according to claim 7, wherein the activematerial layer includes N-methyl-2-pyrrolidone.
 12. A method formanufacturing an electrode for a battery, the method comprising; formingan active material layer on at least one surface of a current collector,forming an insulating layer such that the insulating layer is finallylaminated on a surface of the active material layer, and wherein atleast one of a material of the active material layer, a formationcondition of the active material layer, a material of the insulatinglayer and a formation condition of the insulating layer is determinedsuch that peeling occurs between the current collector and the activematerial layer and a peeling strength thereof is 10 mN/mm or more when a90° peeling test is carried out at a peeling rate of 100 mm/min.
 13. Themethod for manufacturing the electrode according to claim 12, whereinthe step of forming the active material layer comprises: applying amixture for the active material layer in which an active material and abinder are dispersed in a solvent, drying the mixture for the activematerial layer after the mixture is applied, and compression-molding themixture for the active material layer after the mixture is dried, andwherein the step of forming the insulating layer comprises: applying amixture for the insulating layer in which an insulating material and abinder are dispersed in a solvent, drying the mixture for the insulatinglayer after the mixture is applied, and compression-molding the mixturefor the insulating layer after the mixture is dried.
 14. The method formanufacturing the electrode according to claim 13, wherein the step ofapplying the mixture for the active material layer, the step of dryingthe mixture for the active material layer, the step ofcompression-molding the mixture for the active material layer, the stepof applying the mixture for the insulating layer, the step of drying themixture for the insulating layer and the step of compression-molding themixture for the insulating layer are carried out in this order.
 15. Themethod for manufacturing the electrode according to claim 13, whereinthe step of applying the mixture for the active material layer, the stepof drying the mixture for the active material layer, the step ofapplying the mixture for the insulating layer and the step of drying themixture for the insulating layer are carried out in this order, andwherein the step of compression-molding the mixture for the activematerial layer and the step of compression-molding the mixture for theinsulating layer are carried out simultaneously after the step of dryingthe mixture for the insulating layer.
 16. The method for manufacturingthe electrode according to claim 13, wherein the step of applying themixture for the active material layer and the step of applying themixture for the insulating layer are carried out in this order, the stepof drying the mixture for the active material layer and the step ofdrying the mixture for the insulating layer are carried outsimultaneously after the step of applying the mixture for the insulatinglayer, and the step of compression-molding the mixture for the activematerial layer and the step of compression-molding the mixture for theinsulating layer are carried out simultaneously thereafter.
 17. Themethod for manufacturing the electrode according to claim 13, whereinthe mixture for the active material layer includes polyvinylidenefluoride as the binder.
 18. The method for manufacturing the electrodeaccording to claim 13, wherein the mixture for the active material layerincludes N-methyl-2-pyrrolidone as the solvent.